A lithium battery employs, as a negative electrode active material, lithium having a large electronegativity, and it therefore has a characteristic feature such that it can provide a high voltage of about 3 V when a positive electrode formed bv, for example manganese dioxide, carbon fluoride or the like as an active material, is combined with such a negative electrode to form a battery. Accordingly, only one lithium battery is sufficient for a clock using a liquid crystal display in which ordinarily two silver batteries (each supplying 1.5 V) are connected in series to each other. This presents an advantage to simplify the construction of such clock.
In a lithium battery having a negative electrode formed with lithium as the active material and a positive electrode formed with, for example, manganese dioxide as the active material, the discharge reaction is deemed as shown in the following: EQU Mn.sup.IV O.sub.2 +Li.fwdarw.Mn.sup.III O.sub.2 (Li.sup.+)
That is, during the discharge of a lithium battery, lithium of the negative electrode is transferred to the positive electrode and a discharge product is increasingly accumulated at the positive electrode, thereby increasing the internal resistance of the battery.
In order to enhance the coefficient of utilization of the positive electrode, a conventional lithium battery is formed such that the discharge capacity of the negative electrode is larger than that of the positive electrode. Thus, such a conventional lithium battery has been constructed as a positive-dominated battery in which the battery discharge expires upon the consumption of the positive electrode. Therefore, such a conventional lithium battery has had a characteristic such that the drop in voltage during the final discharge stage has been slow.
Accordingly, when such conventional lithium batteries have been used as power supplies for a device using a liquid crystal display, a LSI or the like, such slow voltage drop at the final discharge stage has presented inconveniences.
A liquid crystal display is generally operable at a voltage of about 2.4 V or more and is not operable at a voltage of about 1.8 V or less. Between 1.8 V and 2.4 V, it operates in an unstable manner, thereby possibly provoking an erroneous operation the device with which it is used.
Accordingly, it would not be desirable for a battery to have such a characteristic that a drop in voltage at the final discharge stage is gradual.